P522: ABSOLUTE LYMPHOCYTE COUNT IS AN INDEPENDENT SURVIVAL PREDICTOR IN PATIENTS WITH ACUTE MYELOID LEUKEMIA TREATED WITH INTENSIVE CHEMOTHERAPY
Authors: G. Cristiano, J. Nanni, L. Zannoni, C. Sartor, S. Parisi, S. Paolini, C. Papayannidis, M. Cavo, A. Curti
Journal: HemaSphere (2022)

Background: Absolute lymphocyte count (ALC) is known to be an independent prognostic factor for overall survival (OS) in patients receiving autologous transplantation for Hodgkin’s and non-Hodgkin’s lymphomas, multiple myeloma and breast cancer. In acute myeloid leukemia (AML) patients, enhanced ALC recovery after intensive chemotherapy (IC) has been associated with superior OS and leukemia-free survival (LFS). However, few if any data correlated ALC recovery with novel therapies as well as with updated prognostic factors, such as European Leukemia Net (ELN) risk-classification. Aims: Our study aims at evaluating the predictive value of ALC recovery in AML patients treated with IC by analysing its impact through different patient subgroups according to therapy response, type of chemotherapy regimen and the use of allogeneic stem cell transplantations (HSCT). Methods: We evaluated 148 newly diagnosed adult AML patients treated with IC at Bologna Seràgnoli Hematology Institute since 2007. We defined 4 ALC time-points (TPs): at 15, 21 and 28 days from the start of induction chemotherapy and before consolidation therapy (CC). ALC cut-off was established at 500/mm3. In addition to the assessment of the single TP, patients were also grouped in those who obtained ≥500/mm3 ALC in all 4 TPs and those who had <500/mm3 ALC in at least one TP. Median follow-up was 51,4 months. Results: When ALC recovery was assessed at the single TP, only ALC-CC recovery showed a statistically significant association with better OS and LFS. However, significant outcome differences were observed among CR patients (76,3%), subdivided in those who achieved ALC in all TPs vs others. A trend toward better correlation of ALC with OS was observed in patients who received “3 + 7-based” regimen (30,8%;) versus those who were treated with “fludarabine-based” regimen (69,1%;). Better outcome was observed in “3 + 7” patients who had ALC recovery in all TPs and at day 15 post-chemotherapy. Of note, in the “3 + 7” group, FLT3-ITD positive patients, who achieved early ALC recovery at day 21 had better outcomes. We, then, analysed the impact of post-chemotherapy ALC recovery in patients who received HSCT (66,3%) vs those who did not (33,6%) (Fig.1). As expected, transplanted patients had globally better outcome than patients who received only chemotherapy. In patients who received HSCT the impact of ALC recovery after chemotherapy was minimal. In contrast, patients who had ALC <500/mm3 ALC in at least one TP and did not undergo HSCT had the worst outcome. Interestingly, patients who were not transplanted but had ≥500/mm3 ALC in all 4 TPs had a similar outcome as patients who received HSCT. Image:Summary/Conclusion: Our study indicates ALC recovery after IC as a promising survival predictor in AML patients, especially in those who do not undergo HSCT. In the path that aims to investigate the complex interaction between leukemia and the immune system, our study may provide the clinical rationale for the construction of an immunological score to be integrated in the current disease-centered risk-classification system. Future studies in larger cohorts addressing the impact of ALC recovery in association with the use of novel agents and minimal residual disease status are highly warranted.